diff --git a/moochub-schema.json b/moochub-schema.json
index 82b728a..5492937 100644
--- a/moochub-schema.json
+++ b/moochub-schema.json
@@ -575,80 +575,56 @@
       "type": "object",
       "description": "This schema describes the attributes of a course id. It is used to point at a specific course.",
       "properties": {
-        "name": {
-          "type": "array",
-          "description": "List of names of the course. This array allows localized strings. A name and a language have to be given in the respective element.",
-          "items": {
-            "type": "object",
-            "properties": {
-              "inLanguage": {
-                "type": "string",
-                "description": "The language the name is given in. Has to be a shortcode according to BCP 47.",
-                "example": "en"
-              },
-              "name": {
-                "type": "string",
-                "description": "The name of the course in the given language by the \"inLanguage\" attribute.",
-                "example": "HPI Academy: Leading Digital Transformation and Innovation - Fall 2020"
-              }
-            },
-            "required": [
-              "inLanguage",
-              "name"
-            ]
-          }
-        },
-        "educationalFramework": {
-          "type": "string",
-          "description": "This labels the object as a link to a course. It is needed to be compliant with a \"Skill\" ",
-          "enum": [
-            "Course_ID"
-          ]
-        },
-        "educationalFrameworkVersion": {
+        "title": {
           "type": "string",
-          "description": "This labels the object as a link to a course. It is needed to be compliant with a \"Skill\" ",
-          "example": "Fall 2020"
+          "description": "The name of the course.",
+          "example": "HPI Academy: Leading Digital Transformation and Innovation - Fall 2020"
         },
-        "targetUrl": {
-          "type": "string",
-          "description": "An IRI pointing at a course.",
-          "example": "https://open.hpi.de/courses/digitrans2020-1"
-        }
-      },
-      "required": [
-        "name",
-        "educationalFramework",
-        "educationalFrameworkVersion"
-      ]
-    },
-    "ProgramReference": {
-      "title": "Program",
-      "type": "object",
-      "description": "This schema describes the attributes of a course program to an extend that it links to a EducationalOccupationalProgram.",
-      "properties": {
         "url": {
           "type": "string",
-          "description": "An IRI pointing at the course program or a homepage of the program, ... etc.",
+          "description": "An IRI pointing at the course or program.",
           "format": "iri"
         },
         "type": {
           "type": "string",
-          "description": "The type of the object.",
+          "description": "The type of the referenced object.",
           "enum": [
-            "Program"
+            "Program",
+            "Course"
           ]
-        },
-        "title": {
-          "type": "string",
-          "description": "The title or name of the course program this course is part of."
         }
       },
       "required": [
+        "title",
         "url",
         "type"
       ]
     },
+    "CoursePartReference": {
+      "description": "A course that is part of a program or a course. In addition to the properties of CourseReference, the requirementLevel property is used to indicate if the course is mandatory or elective.",
+      "allOf": [
+        {
+          "$ref": "#/$defs/CourseReference"
+        }
+      ],
+      "properties": {
+        "requirementLevel": {
+          "$ref": "#/$defs/RequirementLevel"
+        }
+      },
+      "required": [
+      	"requirementLevel"
+      ]
+    },
+    "RequirementLevel": {
+      "type": "string",
+      "description": "The level of requirement for this course in the context of the parent course. Can be 'mandatory' or 'elective'.",
+      "enum": [
+        "mandatory",
+        "elective"
+      ],
+      "example": "mandatory"
+    },
     "CompetencyRequirement": {
       "type": "array",
       "description": "A list of competencies that are required to successfully complete this item. This includes skills, certificated, (high) school degrees, other courses",
@@ -1026,9 +1002,10 @@
           },
           "type": {
             "type": "string",
-            "description": "Type of the object.",
+            "description": "Type of the object. 'Course' for individual courses, 'Program' for microdegrees and course programs.",
             "enum": [
-              "Course"
+              "Course",
+              "Program"
             ]
           },
           "attributes": {
@@ -1299,19 +1276,57 @@
               },
               "hasPart": {
                 "type": "array",
-                "description": "A list of the learning items like videos, lectures, quizzes, ... in the course.",
+                "description": "A list of the learning items like videos, lectures, quizzes, ... or courses that make up the course or program (both mandatory and elective).",
                 "uniqueItems": true,
                 "items": {
-                  "$ref": "#/$defs/LearningItem"
+                  "oneOf": [
+                    {
+                      "$ref": "#/$defs/LearningItem"
+                    },
+                    {
+                      "$ref": "#/$defs/CoursePartReference"
+                    }
+                  ]
                 }
               },
               "isPartOf": {
                 "type": "array",
-                "description": "A list of programs (preferable EducationalOccupationalPrograms) this course is part of. The given metadata shall at least contain a link to the program.",
+                "description": "A list of courses or programs (preferable EducationalOccupationalPrograms) this course is part of.",
                 "uniqueItems": true,
                 "example": null,
                 "items": {
-                  "$ref": "#/$defs/ProgramReference"
+                  "$ref": "#/$defs/CourseReference"
+                }
+              },
+              "relatedTo": {
+                "type": [
+                  "array",
+                  "null"
+                ],
+                "description": "A list of relationships this course has with other courses. Uses a simple 2-dimensional approach: sequence type (prequel/sequel/complementary) combined with requirement level (mandatory/recommended). This enables defining course pathways and learning sequences.",
+                "uniqueItems": true,
+                "items": {
+                  "title": "CourseRelationship",
+                  "type": "object",
+                  "description": "Defines a relationship between this course and another course, including the type of relationship and reference to the related course.",
+                  "properties": {
+                    "course": {
+                      "$ref": "#/$defs/CourseReference"
+                    },
+                    "type": {
+                      "type": "string",
+                      "description": "The type of relationship between this course and the related course. Defines the nature of the relationship, such as whether it is a prerequisite, a follow-up, or complementary.",
+                      "enum": [
+                        "foundation",
+                        "continuation",
+                        "complementary"
+                      ]
+                    }
+                  },
+                  "required": [
+                    "course",
+                    "type"
+                  ]
                 }
               }
             }